This invention relates to a coated work rotating apparatus for rotating a coated work such as a bumper for an automobile during drying of a coated film of paint on the work.
In order to provide high grade feeling to an automobile, a degree of coating of a body of the automobile is a very important factor, and various coating techniques have been developed to increase high grade feeling together with improvement in efficiency of coating by individual automobile makers. Also for a bumper, a collapsible bumper made of a synthetic resin is employed in place of a conventional bumper made of sheet metal, and coating is applied to such bumper to increase the high grade feeling of the automobile. A coating process of a bumper made of a synthetic resin generally includes a washing step, a masking step, an undercoating and drying step, and a final coating and drying step.
In order to maintain a quality of coating, it is important to minimize causes of failure in coating. One of causes of failure in coating is a sagging of paint which takes place when a vertical face or an inclined face of a work is coated. As one of causes of such sagging, the thickness of a film of paint is excessively great or the viscosity of paint is excessively low, and if part of paint flows down over several millimeters, then the film of the paint will be swollen and form a sagging mark at a location at which such flow of the paint stops. As countermeasures for preventing a sagging of paint, various methods may be available including, for example, to decrease the thickness of a film of paint, to increase the viscosity of paint and to accelerate drying of paint. Also rotating a coated work for a predetermined period of time immediately after coating of the work is an effective method for preventing the sagging of paint.
For example, U.S. Pat. No. 4,874,639 discloses, under the title of coating method and apparatus on a coating line, a technique of rotating a body of an automobile while transporting the automobile body by means of a transport truck. And, Japanese Laid-Open Patent Publication No. 64-63075 discloses a coating process which includes a drying and baking step wherein a body for an automobile is rocked while it is being rotated.
The techniques disclosed in U.S. Pat. No. 4,874,639 and Japanese Laid-Open Patent Publication No. 64-63075 mentioned above, however, do not provide satisfactory finish of coating because a sagging of paint sometimes takes place due to the fact that all of coated faces of a work are not directed upwardly during rotation of the coated work.